Cryoprobe with warming feature

ABSTRACT

Cryocoolers for use in cryosurgery and other applications comprising finned tube helical coil heat exchangers and warming gas flow through a warming gas supply line fitted Joule-Thomson nozzle. The cryocoolers use helium, hydrogen or neon as a warming gas which is expanded from the Joule-Thomson nozzle to heat the probes.

FIELD OF THE INVENTION

This invention relates to cryocoolers, and to cryoprobes for use incryosurgery.

BACKGROUND OF THE INVENTION

Cryosurgical probes are used to treat a variety of diseases. Thecryosurgical probes quickly freeze diseased body tissue, causing thetissue to die after which it will be absorbed by the body or expelled bythe body or sloughed off. Cryothermal treatment is currently used totreat prostate cancer and benign prostate disease, breast tumors andbreast cancer, liver tumors and cancer, glaucoma and other eye diseases.Cryosurgery is also proposed for the treatment of a number of otherdiseases.

The use of cryosurgical probes for cryoablation of the prostate isdescribed in Onik, Ultrasound-Guided Cryosurgery, Scientific American at62 (January 1996) and Onik, Cohen, et al., Transrectal Ultrasound-GuidedPercutaneous Radial Cryosurgical Ablation Of The Prostate, 72 Cancer1291 (1993). In this procedure, generally referred to as cryoablation ofthe prostate, several cryosurgical probes are inserted through the skinin the perineal area (between the scrotum and the anus) which providesthe easiest access to the prostate. The probes are pushed into theprostate gland through previously place cannulas. Placement of theprobes within the prostate gland is visualized with an ultrasoundimaging probe placed in the rectum. The probes are quickly cooled totemperatures typically below -120° C. The prostate tissue is killed bythe freezing, and any tumor or cancer within the prostate is alsokilled. The body will absorb some of the dead tissue over a period ofseveral weeks. Other necrosed tissue may slough off through the urethra.The urethra, bladder neck sphincter and external sphincter are protectedfrom freezing by a warming catheter placed in the urethra andcontinuously flushed with warm saline to keep the urethra from freezing.

Rapid re-warming of cryosurgical probes is desired. The cryosurgicalprobes are warmed to promote rapid thawing of the prostate, and uponthawing the prostate is frozen once again in a second cooling cycle. Theprobes cannot be removed from frozen tissue because the frozen tissueadheres to the probe. Forcible removal of a probe which is frozen tosurrounding body tissue leads to extensive trauma. Thus manycryosurgical probes provide mechanisms for warming the cryosurgicalprobe with gas flow, condensation, electrical heating, etc.

A variety of cryosurgical instruments, variously referred to ascryoprobes, cryosurgical ablation devices, and cryostats andcryocoolers, have been available for cryosurgery. The preferred deviceuses Joule-Thomson cooling in devices known as Joule-Thomson cryostats.These devices take advantage of the fact that most gases, when rapidlyexpanded, become extremely cold. In these devices, a high pressure gassuch as argon or nitrogen is expanded through a nozzle inside a smallcylindrical sheath made of steel, and the Joule-Thomson expansion coolsthe steel sheath to sub-freezing cryogenic temperature very rapidly.

An exemplary device is illustrated in Sollami, Cryogenic SurgicalInstrument, U.S. Pat. No. 3,800,552 (Apr. 2, 1974). Sollami shows abasic Joule-Thomson probe with a sheath made of metal, a fin-tubehelical gas supply line leading into a Joule-Thomson nozzle whichdirects expanding gas into the probe. Expanded gas is exhausted over thefin-tube helical gas supply line, and pre-cools incoming high pressuregas. For this reason, the coiled supply line is referred to as a heatexchanger, and is beneficial because, by pre-cooling incoming gas, itallows the probe to obtain lower temperatures.

Ben-Zion, Fast Changing Heating and Cooling Device and Method, U.S. Pat.No. 5,522,870 (Jun. 4, 1996) applies the general concepts ofJoule-Thomson devices to a device which is used first to freeze tissueand then to thaw the tissue with a heating cycle. Nitrogen is suppliedto a Joule-Thomson nozzle for the cooling cycle, and helium is suppliedto the same Joule-Thomson nozzle for the warming cycle. Preheating ofthe helium is presented as an essential part of the invention, necessaryto provide warming to a sufficiently high temperature.

A Joule-Thomson cryostat for use as a gas tester is illustrated inGlinka, System for a Cooler and Gas Purity Tester, U.S. Pat. No.5,388,415 (Feb. 14, 1995). Glinka also discloses use of the by-pass fromthe Joule-Thomson Nozzle to allow for cleaning the supply line, and alsomentions that the high flow of gas in the by-pass mode will warm theprobe. This is referred to as mass flow warming, because the warmingeffect is accomplished purely by conduction and convection of heat tothe fluid mass flowing through the probe.

Various cryocoolers use mass flow warming, flushed backwards through theprobe, to warm the probe after a cooling cycle. Lamb, RefrigeratedSurgical Probe, U.S. Pat. No. 3,913,581 (Aug. 27, 1968) is one suchprobe, and includes a supply line for high pressure gas to aJoule-Thomson expansion nozzle and a second supply line for the same gasto be supplied without passing through a Joule-Thomson nozzle, thuswarming the catheter with mass flow. Longsworth, Cryoprobe, U.S. Pat.No. 5,452,582 (Sep. 26, 1995) discloses a cryoprobe which uses thetypical fin-tube helical coil heat exchanger in the high pressure gassupply line to the Joule-Thomson nozzle. The Longsworth cryoprobe has asecond inlet in the probe for a warming fluid, and accomplishes warmingwith mass flow of gas supplied at about 100 psi. The heat exchanger,capillary tube and second inlet tube appear to be identical to thecryostats previously sold by Carleton Technologies, Inc. of OrchardPark, N.Y.

Each of the above mentioned cryosurgical probes builds upon prior artwhich clearly establishes the use of Joule-Thomson cryocoolers, heatexchangers, thermocouples, and other elements of cryocoolers. Walker,Miniature Refrigerators for Cryogenic Sensor and Cold Electronics (1989)(Chapter 2) and Walker & Bingham, Low Capacity Cryogenic Refrigeration,pp. 67 et seq. (1994) show the basic construction of Joule-Thomsoncryocoolers including all of these elements. The Giaque-Hampson heatexchanger, characterized by coiled finned-tube, transverse flowrecuperative heat exchanger is typical of cryocoolers. The open mandrelaround which the finned tube coil is placed is also typical ofcryocoolers.

Cryosurgical probes may be used, as mentioned above, to treat diseasesof the prostate, liver, and breast, and they have gynecologicalapplications as well. The cryosurgical probes form iceballs which freezedisease tissue. Each application has a preferred shape of iceball,which, if capable of production, would allow cryoablation of thediseases tissue without undue destruction of surrounding healthy tissue.For example, prostate cryoablation optimally destroys the lobes of theprostate, while leaving the surrounding neurovascular bundles, bladderneck sphincter and external sphincter undamaged. The prostate is widerat the base and narrow at the apex. A pear or fig shaped ice ball isbest for this application. Breast tumors tend to be small and spherical,and spherical iceballs will be optimal to destroy the tumors withoutdestroying surrounding breast tissue. Liver tumors may be larger and ofa variety of shapes, including spherical, olive shaped, hot dog shapedor irregularly shaped, and may require more elongated iceballs, largericeballs, and iceballs of various shapes.

SUMMARY

The heat exchanger comprises a Giaque-Hampson heat exchanger with finnedtube gas supply line coiled around a mandrel. After expansion in the tipof the cryoprobe, the gas flows over the coils and exhausts out theproximal end of the probe. The flow of exhaust gas over the heatexchanger coils is controlled by placement of a flow directing sheathplaced in different longitudinal areas of the heat exchanger. To createspherical iceballs, the thermal barrier is placed over the entire lengthof the heat exchanger coil. To create pear shaped iceballs, the flowdirecting sheath is place over the proximal portion of the coil, but notover the distal portion of the coil. For an elongate cylindricaliceball, which we call hot dog shaped, the flow directing sheath isplaced over the proximal end of the heat exchanger coil, but not overthe distal end of the coil, and the nozzle is placed proximally from thecryoprobe tip. Alternative embodiments include variation of the lengthof the straight supply tube extending distally from the helical coilheat exchanger, and variation of the distance of the Joule-Thomsonnozzle from the distal tip of the probe.

These shapes are desired for the several shapes of tissues that aresubject to cryosurgical treatment. The olive-shaped and pear-shapediceballs are useful for prostate treatment, as they permit creation ofthe optimal iceball within the prostate. The spherical iceball isdesired for treatment of breast tumors, which tend to be spherical. Theoblong iceball is desired for treatment of liver tumors, which tend tobe oblong. Of course, the correspondence of the shapes to the anatomicalsite is not a hard and fast rule, and each shape of iceball will beuseful in any area of the body wherein a tumor or other conditionindicates use of a particular shape.

Parallel finned tubes are used in one embodiment to create a dual helixdesign. In this embodiment, two parallel gas supply lines are used, andthey are wound in parallel around the mandrel. The nozzles tips may belocated equidistant from the tip of the probe for a spherical iceball,and they may be offset, with one nozzle placed distally of the other tocreate an oblong iceball. Both of the dual coils can be used to supplyhigh pressure gas which cools upon expansion (nitrogen, argon, NO2, CO2,etc.), so that both coils are used for cooling. One coil can be used forcooling gas while the other coil is used for the supply of a highpressure gas which heats upon expansion (hydrogen, helium, and neon).

Separate cooling and heating Joule-Thomson nozzles are used in anembodiment wherein the heating gas is supplied through the mandrel. Inthis embodiment, the heating gas supply is not subject to heat exchangewith the exhausting heating gas to create a higher initial heating rate.To permit complete control of both heating and cooling, the severalcryoprobes are supplied with gas through a dual manifold which allowsfor independently warming each probe. This allows removal of individualprobes in case the doctor performing the cryosurgery decides that acryoprobe must be moved after it has formed an iceball. It also allowsprotective warming for nearby anatomical structures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic drawing of the probes of the present invention inuse in the transperineal cryosurgical ablation of the prostate.

FIG. 2 is a view of the cryosurgical probe including the tubingconnecting the probe to gas supplies.

FIG. 3 is a cross section of the cryosurgical probe adapted to provide apear shaped iceball

FIG. 4 is a cross section of the cryosurgical probe adapted to provide aoblong or olive-shaped iceball.

FIG. 5 is a cross section of the cryosurgical probe adapted to provide aspherical iceball.

FIG. 6 is a cross section of the cryosurgical probe adapted to providecylindrical iceball.

FIG. 7 is a cross section of the cryosurgical probe with parallel fintubing and flow directing sheaths located inside and outside the heatexchanger coil.

FIG. 8 is a cross section of the cryosurgical probe with parallel fintubing.

FIG. 9 is a cross section of the cryosurgical probe with parallel fintubing and offset dual Joule-Thomson nozzles.

FIG. 10 is a cross section of the cryosurgical probe with parallel fintubing, adapted for use of one coil for cooling and one coil forheating.

FIG. 11 is a cross section of the cryosurgical probe with a heliumJoule-Thomson nozzle.

FIG. 12 is a cross section of the cryosurgical probe with longitudinallyoffset heat exchangers for the cooling and warming gas flow.

FIG. 13 is a cross section of the cryosurgical probe with parallel fintubing and a coaxial heating nozzle.

FIG. 14 is a cross section of the cryosurgical probe with longitudinallyoffset heat exchangers and longitudinally offset Joule-Thomson expansionnozzles.

FIGS. 15 and 16 schematics of the manifolds used for operation of thecryosurgical probe.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows one of the basic operations for which the cryoprobes aredesigned. Several probes 1a, 1b, and 1c are shown inserted in theprostate 2. All three probes are inserted through the perineal region 3between the scrotum and the anus. Probe 1a is shown inserted into theanterior lobe 2a of the prostate, and Probes 1b and 1c are showninserted into the posterior lobe 2b, which is larger than the anteriorlobe. The probes are placed within the prostate according to procedureswell known in the art, and a suitable procedure is described instep-by-step detail in Onik, et al., Percutaneous Prostate Cryoablation,(1995) at pages 108-112 and Onik, Ultrasound-Guided Cryosurgery,Scientific American at 62. (January 1996). The urethra 4 which passesthrough the prostate is one of the anatomic structures that usuallyshould not be frozen during this surgery. Accordingly, the urethra isprotected and kept warm with the urethral warming catheter 5. Thebladder neck sphincter 6 and the external sphincter are also structuresthat should be protected from freezing, and these are protected fromfreezing by the warming catheter. Neurovascular bundles on the right andleft of the prostate should also be protected from freezing. Transrectalprobe 8 is inserted into the rectum 9 in order to visualize theplacement of the probes and the growth of the iceballs formed by thecryoprobes.

FIG. 2 shows the entire cryosurgical probe assembly. The cryoprobe 1includes a cryocooler 10 about 25 cm (10 inches) long and 3.5 mm (0.134in.) in diameter. These sizes are convenient and preferred forcryoprobes intended for prostate use, and may vary widely. The probeouter sheath 11 houses the cryostat described in detail below. A handle12 of convenient size is provided. The flexible tube 13 houses gassupply lines 14 and thermocouple electrical wiring 15, and has a vent 16for exhaust gas. The gas supply line is connected to a high pressure gassupply through high pressure fitting 17. The thermocouple wire isconnected to the control system through electrical connector 15.

The details of the cryostat used in the cryosurgical probe areillustrated in FIGS. 3 through 6. FIG. 3 shows the basic embodiment ofthe cryosurgical probe. The high pressure gas supply line 14 connects tothe proximal extension 19 of the finned tube coiled heat exchanger 20.The heat exchanger extends longitudinally through the outer sheath 11and connects to the cooling fluid outlet comprising distal extension 21which open through Joule-Thomson nozzle 22 into expansion chamber 23.The expansion chamber size and shape is controlled in part by the innersurface of the distal end plug and thermal barrier 24 which seals theouter sheath 11 and closes the distal end of the sheath. The outersheath is made of thermally conductive material such as stainless steel.The end plug may take many shapes but preferably has a rounded outercontour and a convex inner surface as shown. The end plug may be made ofstainless steel, or it may be made of tantalum, titanium, ceramic orother relatively insulating material to inhibit heat transfer from thetip of the probe. The heat exchanger is coiled around mandrel 25. Thedistal endpoint of the mandrel and the distal endpoint of theJoule-Thomson nozzle are equidistant from the end plug. In between eachwinding of the heat exchanger, gaps 26 are formed between the coil andthe outer sheath, and gaps 27 are formed between the coil and themandrel. This construction is known as a Giaque-Hampson heat exchanger.

The heat exchanger, which is an integral part of the high pressure gaspathway, is made with finned tubing, with numerous fins 28 throughoutits length. The finned tubing is approximately 30 cm (12 inches) longand 0.75 mm (0.030 in.) in outer diameter and the fins are approximately1 mm (0.0437 in.) in diameter. The finned tube coil is wrapped aroundthe mandrel for 18 turns or so. The fins are stripped from the proximalextension for a length sufficient to allow insertion of the finnedtubing into high pressure line 14 and soldering of the high pressureline to the finned tube. The mandrel is 0.75 mm.(0.032 in.) in outerdiameter and 10 cm (3.75 in.) long. The Joule-Thomson nozzle isapproximately 1.5 mm (0.0625 in.), with an internal diameter of 0.2 mm(0.008 in.). At the distal tip of the mandrel is a thermocouple 29 whichis used to measure and monitor the temperature inside the cryosurgicalprobe.

Control of the iceball shape is accomplished primarily with the flowdirecting sheath 30. The flow directing sheath shown in FIG. 3 isconveniently made of a heat shrink tube 3.25 cm (1.5 in.) long and 0.03mm (1.75 mils) thick. The flow directing sheath surrounds the heatexchanger coil and is generally coaxially disposed about the heatexchanger. In the preferred embodiment, the flow directing sheathprotrudes radially into the interstitial ridges between the windings orturns of the heat exchanger coil, as illustrated in FIG. 3 and the otherfigures illustrating the flow directing sheath. The flow directingsheath lengthens the gas flow path and forces gas to flow past the finsof the finned tube rather than flowing through the interstitial ridgesbetween the turns of the helix. The sheath 30 also serves as a thermalbarrier, isolating and/or insulating the outer sheath 11 from the coldexpanded gas flowing over the finned tube heat exchanger. This thermalbarrier can be customized during manufacture to control the heatexchange characteristics of the probe and thereby control the shape ofthe iceball created by the probe. The length and number of windingscovered by the flow directing sheath/thermal barrier is predeterminedbased on the desired iceball shape for which each probe is made.

Fluid flow through the cryosurgical probe is as follows. High pressurefluid, preferably gaseous nitrogen or argon, and preferably at apressure of about 3000 psi, is supplied to the assembly through highpressure fitting 17, flows through gas supply line 14, into heatexchanger 20 and through cooling fluid outlet 21 and Joule-Thomsonnozzle 22. The high pressure gas expands within the expansion chamberand cools to cryogenic temperatures. Condensation of the gas ispreferably avoided but can be tolerated. After expanding, the gas is atlower pressure and exhausts over the exhaust gas pathway which includesflow over outside of the coils of the heat exchanger 20. Because it isnow cold, it cools the gas flowing inside the coils. This makes coolingmore efficient and allows use of less gas. While flowing over theoutside of the finned tube, the gas is directed away from the inside ofthe outer sheath 11 thus preventing any significant heat exchange withthe outer sheath. After passing through the heat exchanger, the exhaustgas flows through the remainder of the exhaust gas pathway whichincludes the flexible tube and the vent 16 which vents the exhaust gasto atmosphere.

Various modifications of the flow directing sheath 30 allow creation ofvarious iceball shapes. For convenience of reference, we refer threelongitudinal segments of the helical coils as distal segment, centralsegment, and proximal segment. In FIG. 3, the flow directing sheathcovers the proximal portion 31 and central portion 32 of the heatexchanger, and the distal portion 33 of the heat exchanger is leftuncovered. The distance L3 between the Joule-Thomson nozzle and the endof the heat exchange chamber is approximately 5 mm (0.2 in.). The lengthL2 of the distal extension 21 of the heat exchanger is approximately 7.5mm (0.30 in.). The length of the heat exchanger coil L1 is approximately5 cm (2 in.). Operation of this cryosurgical probe within the body willcreate an ice ball having a pear shape. FIG. 3 also includes a thermalinsulating end plug made of a material that is less thermally conductivethan the stainless steel outer sheath in order to block heat transfer atthe distal tip of the probe and thereby promote a flatter bottom for thepear shaped iceball.

In FIG. 5, the flow directing sheath is applied over substantially theentire length of the heat exchanger coil. The distance L3 between theJoule-Thomson nozzle and the end of the heat exchange chamber isapproximately 5 mm (0.2 in.). The length L2 of the distal extension 21of the heat exchanger is approximately 8 mm (0.3 in.). Operation of thiscryosurgical probe within the body creates an iceball with a oliveshape. In FIG. 5, the flow directing sheath is applied oversubstantially the entire length of the heat exchanger coil. The distanceL3 between the Joule-Thomson nozzle and the end of the heat exchangechamber is approximately 2.5 mm (0.1 in.), significantly shorter thanthat shown for FIG. 4a. The length L2 of the distal extension 21 of theheat exchanger is approximately 5 mm (0.2 in.). Operation of thiscryosurgical probe within the body creates an iceball with a oliveshape.

In FIG. 6, the flow directing sheath covers only the proximal portion ofthe helical coil. The distance L3 between the Joule-Thomson nozzle andthe end of the heat exchange chamber is significantly longer that thatshown in FIG. 5, approximately 5 mm (0.2 in.). The length L2 of thedistal extension 21 of the heat exchanger is approximately 12.5 mm (0.6in.). Operation of this cryosurgical probe within the body will createan ice ball having a hot dog shape.

Illustrated in FIG. 7 is an embodiment wherein the flow directing sheathis augmented with a second flow directing sheath 34 placed coaxiallybetween the heat exchanger coils and the mandrel. The second flowdirecting sheath can be made with impressible material such as teflon,or may be integrally formed with the mandril. The inside sheath blocksflow through the gaps between the coils and forces all gas flow to passthe fins, thus promoting heat transfer. Thus it can be appreciated thatthe sheaths serve to block gas flow from flowing through the gapsbetween the windings and promotes more efficient heat exchange, afunction previously accomplished by threads wrapped in the gaps, inparallel with the coils.

FIG. 8 shows a cryosurgical probe which includes two coiled heatexchangers and two Joule-Thomson nozzles. This dual helix cryosurgicalprobe produces large iceballs. The high pressure gas supply line 14 andfinned tube helical coil heat exchanger 20 are the same as thosedescribed in reference to the preceding figures. A second high pressuregas supply line 35, heat exchanger 36, gas outlet 37 and Joule-Thomsonnozzle 38 are provided. High pressure gas is expanded through bothJoule-Thomson nozzles 22 and 38. The helical coils are parallel to eachother, meaning that the coils follow the same helical path around themandrel. When the Joule-Thomson nozzles are located at the samelongitudinal location, a large spherical iceball can be formed veryrapidly. When the Joule-Thomson nozzles are offset or staggered, meaningthat the longitudinal placement of each nozzle is significantlydifferent, the probe very rapidly forms a cylindrical iceball. Thecryosurgical probe having two parallel helical coils with gas outletthat are equidistant from the distal tip of the probe is illustrated inFIG. 7. This probe produces a large spherical iceball, and withadjustment of the flow directing sheath can be modified to produce apear shaped or tear-drop shape. The cryosurgical probe having twoparallel helical coils with gas outlets that are offset, with one gasoutlet located distal of the other, and thus closer to the distal tip ofthe probe is illustrated in FIG. 9. This probe with offset Joule-Thomsonnozzles produces a large hot dog shaped iceball.

In reference to all the above cryosurgical probes, it is beneficial tohave a means for warming the probe quickly. This is desired fortherapeutic and practical reasons. Current theory suggests that twocycles of rapid freezing and thawing provides better cryoablation than asingle freeze. Practically, it can take a long time for the iceball tothaw so that the probe can be withdrawn from the body. Unless naturalthawing is medically indicated, natural thawing is a waste of time.

Prior art warming methods such as exhaust blocking, reverse flow heattransfer, and electrical heating can be employed. The preferred methodof warming is to supply high pressure helium gas through the supplyline, heat exchanger and Joule-Thomson nozzle. Helium gas is one of thefew gases that heat up when expanded through the gas outlet. Thus, thesupply of gas to the probes shown in FIGS. 3 through 9 can be switchedfrom high pressure nitrogen or argon to high pressure helium to effectrapid re-warming of the catheter.

The dual helix embodiment shown in FIGS. 8 and 9 may be modified so thathelium may be injected through one supply line aligned only to thehelium gas supply, while the other supply line is used only for supplyof high pressure cooling gas. This embodiment is shown in FIG. 10, whichincludes at the proximal end of the flexible tube a high pressurefitting 17 for the cooling gas (nitrogen, argon, CO₂, etc.) to thecooling gas supply line 39 and a separate high pressure fitting 40 forhelium supply to the warming gas supply line 41. In this embodiment, onesupply line, including the heat exchanger 20, gas outlet 21 andJoule-Thomson nozzle 22 is used to cool the probe with a cooling gas,while the second supply line including heat exchanger 36, gas outlet andJoule-Thomson nozzle 38 is used to heat the probe with warming gas. Thisembodiment is advantageous because the use of the regenerative heatexchanger for the warming gas makes the heating cycle more efficient.

In the embodiment shown in FIG. 11, the mandrel 25 also houses a warminggas supply line 41 with a warming gas outlet 42 and Joule-Thomson nozzle43 injected high pressure heating gas into expansion chamber 23. Thewarming gas supply line and warming gas outlet extend longitudinallythrough the center of heat exchanger 20. Helium gas flowing out of thegas outlet into the expansion nozzle gets hotter when in expands andwarms the probe. The hot expanded helium then flows proximally over theheat exchanger coils of the cooling gas supply line. However, whileheating gas is supplied through heating gas supply line 39, no coolinggas is supplied to the cooling gas supply line. Because no heatexchanger is provided in the warming gas supply line 41, exhausted andhot warming gas does not exchange heat with incoming warming gas that isstill at room temperature within the supply line. This is beneficialbecause the initial blast of warming gas will be cooled well below roomtemperature by the cryogenic temperature of the probe, and heat exchangeof this cold gas with incoming warming gas would lower the temperatureof the incoming warming gas and result in slower re-warming. Absence ofthe heat exchanger in the warming gas supply line thus promotes rapidinitial warming of the probe. This may be a concern only for the initialpulse of warming gas. After the exhaust flow has heated the probe to thepoint where exhausting warming gas is warming the incoming warming gas,a heat exchanger may prove beneficial. Delayed heat exchange may beaccomplished by providing the heating gas supply line 41 with a coiledheat exchanger 44 located well proximally of the warming gas outlet 42,as illustrated in FIG. 12. The warming gas heat exchanger 44 is locatedseveral inches proximal of the coiled heat exchanger 20 in the coolinggas supply line. The warming gas outlet 42 extends longitudinallythrough the cooling gas heat exchanger 20. By providing a longitudinallyoffset heat exchanger for the warming gas supply line, a long initialpulse of warming gas is supplied without heat exchange, but heatexchange is provided in the steady state operation of the warming mode.

The cryosurgical probe of FIG. 13 combines the double helix design withthe mandrel heating supply line. Cooling gas supply line 39 suppliescooling gas to both helical coils through junction 45 and supply linebranches 14a and 14b. Cooling gas is provided through single highpressure fitting 17. The warming gas supply line 41 provides warming gasto the gas outlet 42 and Joule-Thomson nozzle 43 to warm the probe. Thusthe large and rapid iceball formation enabled with the probe of FIGS. 8and 9 is combined with the non-preheated warming flow of FIG. 11. FIG.14 illustrates another embodiment of a cryosurgical probe which providescooling flow and warming flow. The heat exchanger 46, gas outlet 47 andJoule-Thomson nozzle 48 in the warming gas supply line is locatedproximally of the heat exchanger 20, gas outlet 21 and Joule-Thomsonnozzle 22 in the cooling gas supply line. This probe facilitatesformation of oblong iceballs.

The flow of warming gas can be adjusted and modified. As presentedabove, the warming gas flow provides heating or warming sufficient torapidly heat the iceball and melt it. The warming gas flow pathway maybe modified to create heating sufficient to cause thermal necrosis ofsurrounding tissue.

The gas supply system for the cryoprobes is shown schematically in FIG.15. High pressure cooling gas is stored in tank 49, and high pressureheating gas is stored in tank 50. Cooling gas such as nitrogen or argonis stored in the flask at 6000 psi and stepped down to about 3200 psi bypressure regulator 51 and supplied to the gas regulating manifold 52.High pressure heating gas (helium) is stored in the flask at 3000 psiand passed through pressure regulator 51a to the gas regulatingmanifold. Inside the gas regulating manifold, both supply lines areprovided with filters 53 and 54 and banks 55 and 56 or solenoid operatedcut-off valves. The cooling gas supply line regulator 51 is set at 3000psi. The heating gas supply line regulator 51a is set at 1000 psi. Bothmanifold supply lines 59 and 60 are provided with pressure reliefs 61and 62 and various check valves as needed. Gas is supplied to theappropriate cryosurgical probes 13, not shown, gas dispensing manifolds.The cooling gas dispensing manifold has a manifold of solenoid operatedvalves 67 for supply of high pressure cooling gas from manifold supplyline 59 to the probe supply lines 39. The heating gas manifold ofsolenoid operated valves 67 supplies high pressure heating gas from themanifold supply line 60 to the various probe supply lines 39. In thepreferred cryosurgical control system, eight individual probes aresupplied. The probes cool and warm in response to cooling and warminggas through the probes, as controlled by the manifolds. As illustrated,the cooling of each cryosurgical probe in a set of probes can beindependently controlled and the warming of each probe in the set ofprobes can be independently controlled. When the probes make use of asingle supply lines such as supply lines 14 indicated in FIG. 15, thedual manifold can be replaced by a series of three way valves which canalternatively connect the probe supply line 14 to the cooling or heatinggases.

FIG. 16 shows a suitable manifold for independent control of cooling andwarming of cryosurgical probes with separate supply lines for coolingand heating gases, such as the probes illustrated in FIGS. 9, 10 and 11.The cooling gas manifold connects the cooling gas manifold supply lineto the various probe supply lines 14. The warming gas manifold connectsthe warming gas supply line to the various probe warming gas supplylines 39. Again, the separate solenoid operated valves may be replacedwith combination valves such as four way valves so that a single valvecan be used to control flow of cooling gas and warming gas.

In the area of prostate cryoablation, several cryoprobes are usedtogether in a single procedure. In the embodiment illustrated in FIGS.15 and 16, eight cryoprobes are provided for each procedure. For avariety of reasons, it is beneficial to be able to cool each probeseparately, and this feature is provided in current cryoablationsystems. During the same procedure, it is also desirable to re-warm thecryosurgical probes independently, to protect anatomic features thatseem in danger of freezing (as viewed in the transrectal ultrasound) orto change the position of a probe. The dual manifold illustrated inFIGS. 15 and 16 permit such independent control of the re-warming of theprobes.

The gases indicated for use include nitrogen, argon, NO₂, and CO₂ foruse as the cooling gas. These gases are preferred for their readyavailability and safety. In theory, any gas which heats up when expandedmay be used, and some environments may call for gasses such as oxygen,air, and other gasses. The gas indicated for cooling is preferablyhelium, but hydrogen and neon are also known to heat up when expandedand may be used in appropriate environments. Hydrogen and oxygen, weexpect, will be avoided because their use in most environments willcreate an unacceptable risk of explosion. The device described abovehave been developed within the environment of cryosurgery, however thebeneficial features will be useful in other environments of use such aselectronics cooling and gas testing devices and other areas. Thus, whilethe preferred embodiments of the devices and methods have been describedin reference to the environment in which they were developed, they aremerely illustrative of the principles of the inventions. Otherembodiments and configurations may be devised without departing from thespirit of the inventions and the scope of the appended claims.

I claim:
 1. A cryocooler comprising:An outer sheath comprising a tubehaving a closed distal end defining an expansion chamber; a first highpressure gas supply line extending into the outer sheath, said firsthigh pressure gas supply line having a distal end with a Joule-Thomsonexpansion nozzle thereon, said Joule-Thomson nozzle communicating withthe expansion chamber; a supply of high pressure cooling gas operablyconnected to the first high pressure gas supply line; a second highpressure gas supply line extending into the outer sheath, said secondhigh pressure gas supply line having a distal end with a Joule-Thomsonexpansion nozzle thereon, said Joule-Thomson nozzle communicating withthe expansion chamber; a supply of high pressure warming gas operablyconnected to the second high pressure gas supply line.
 2. The device ofclaim 1 wherein the high pressure cooling gas supply line includes afinned tube helical coil heat exchanger, and the high pressure warminggas supply line passes longitudinally through the helical coil heatexchanger.
 3. The device of claim 1 wherein the high pressure warminggas supply line includes a finned tube helical coil heat exchanger. 4.The device of claim 1 wherein:the high pressure cooling gas supply lineincludes a finned tube helical coil heat exchanger; the high pressurewarming gas supply line includes a finned tube helical coil heatexchanger; the coil of the high pressure cooling gas supply line and thecoil of the high pressure warming gas supply line are longitudinallyoffset.
 5. A cryocooler comprising:An outer sheath comprising a tubehaving a closed distal end defining an expansion chamber; a highpressure cooling gas supply line having a distal end with aJoule-Thomson expansion nozzle thereon, said Joule-Thomson nozzlecommunicating with the expansion chamber, said high pressure cooling gassupply line including a finned tube helical coil heat exchanger; asupply of high pressure cooling gas operably connected to the highpressure cooling gas supply line; a high pressure warming gas supplyline having a distal end with a Joule-Thomson expansion nozzle thereon,said Joule-Thomson nozzle communicating with the expansion chamber,wherein said high pressure warming gas supply line passes longitudinallythrough the helical coil heat exchanger; a supply of high pressurewarming gas operably connected to the high pressure warming gas supplyline.
 6. A cryocooler comprising:An outer sheath comprising a tubehaving a closed distal end defining an expansion chamber; a highpressure cooling gas supply line having a distal end with aJoule-Thomson expansion nozzle thereon, said Joule-Thomson nozzlecommunicating with the expansion chamber; a supply of high pressurecooling gas operably connected to the high pressure cooling gas supplyline; a high pressure warming gas supply line having a distal end with aJoule-Thomson expansion nozzle thereon, said Joule-Thomson nozzlecommunicating with the expansion chamber; a supply of high pressurewarming gas operably connected to the high pressure warming gas supplyline; said high pressure warming gas supply line including a finned tubehelical coil heat exchanger.
 7. A cryocooler comprising:An outer sheathcomprising a tube having a closed distal end defining an expansionchamber; a high pressure cooling gas supply line having a distal endwith a Joule-Thomson expansion nozzle thereon, said Joule-Thomson nozzlecommunicating with the expansion chamber; a supply of high pressurecooling gas operably connected to the high pressure cooling gas supplyline; a high pressure warming gas supply line having a distal end with aJoule-Thomson expansion nozzle thereon, said Joule-Thomson nozzlecommunicating with the expansion chamber; a supply of high pressurewarming gas operably connected to the high pressure warming gas supplyline:wherein the high pressure cooling gas supply line includes a finnedtube helical coil heat exchanger; and the high pressure warming gassupply line includes a finned tube helical coil heat exchanger; and thecoil of the high pressure cooling gas supply line and the coil of thehigh pressure warming gas supply line are longitudinally offset.